need some advice

When I was 25, I was in the ROTC program at school trying to get into the Navy. During physical training, I snapped my knee cap out of play. I wanted to go into the Navy so bad, I snapped my knee cap back and kept going. The medical program thought it'd be best for me to keep my feet up for a month. This made my knees stiffer and started a snowball affect into the weight problem I have now. My bad knee is now my worse knee, and my good one is now bad. They both lock up and scream with paid whenever I walk or stand for a long time. I'm currently losing about 5-10 pounds a month with diet and walking when my legs allow. I need to lose this weight faster to get healthy. Does anyone have any advise on exercises I can do?